The present invention relates to a method of manufacturing a magnetic head for a magnetic disk drive unit, etc., and more precisely relates to a method of manufacturing a magnetic head, which is capable of preventing warping of a wafer during the wafer process and for preventing warping of slider blocks formed by cutting the wafer.
In the steps of manufacturing magnetic heads, magnetic head elements are formed by forming films on a front surface of a wafer, then a rear surface of the wafer is ground so as to define a size of sliders. Successively, the wafer is cut to form a plurality of slider blocks, in each of which a plurality of the magnetic head elements are linearly arranged. Floating rails are respectively formed in cut faces of the slider blocks, followed with a plurality of sliders being formed by cutting each slider block.
FIG. 6 show a conventional method of grinding the rear surface of the wafer 10, in which the films have been formed on the front surface. FIG. 6A shows a section of the wafer 10 and a film face 10a. The original wafer 10 is a flat disk, but the front surface of the wafer, on which the films have been formed, is projected by stress in the films. Thus, the wafer 10 must be held parallel to a standard face of a chuck 12, and the rear surface of the wafer 10 is ground so as to correctly define the size.
The wafer 10 is held on the chuck 12 by mechanical means, such as vacuum means or an adhesive (e.g., wax). FIG. 7 shows the mechanical means in which the wafer 10 is held on the chuck 12 by chucking presses 13. FIG. 8 shows the vacuum means in which air is sucked toward a bottom side of the chuck 12 so as to hold the wafer 10, and an outer edge of the wafer is sealed by rubber members 14.
Even if the outer edge of the wafer 10 is held by the mechanical means or the vacuum means so as to be securely set in a grinding machine, a center part of the wafer 10, which has been set in the grinding machine, is sometimes warped. When the rear surface of the wafer 10 is ground, the wafer 10 is pressed onto a grinding face so as to straighten the warping of the wafer 10 as shown in FIG. 6B. However, the thickness of the center part of the wafer 10 is not equal to that of the outer edge thereof as shown in FIG. 6C if the warped wafer 10 is ground.
If the thickness of the wafer 10 is partially different, the size of the sliders disperses. As shown in FIG. 9, the sliders 16 are formed by cutting the slider block, which has been cut from the wafer 10, with regular separations so the size of the slider 16a, located in the center part of the wafer 10, is bigger than that of the slider 16b located in the outer edge.
On the other hand, in the case that the warping of the wafer 10 is straightened and the wafer is ground with uniform thickness, the films are formed on one side of the wafer 10, so imbalanced stress is left in the wafer 10 and the slider blocks must be warped after they are cut from the wafer 10.
In FIG. 10, the floating rails 20 are formed on a disk-side face of the slider block 18, which has been cut from the wafer 10. In FIG. 10A, the slider block 18 is warped, but in FIG. 10B, the slider block 18 is not warped. Since the floating rails 20, each of which has a prescribed pattern, are formed in the slider block 18, in the case of the warped slider block 18 shown in FIG. 10A, the floating rails 20 are shifted from predetermined positions so that the desired floating property cannot be realized.
In FIG. 11, a slope section 15 is formed at a corner of a disk-side face of the slider 16. When the slope section 15 is formed by abrading the corner of the slider block 18, if the slider block 18 is warped as shown in FIG. 11B, the size of the slope section 15 of the slider located at the center part of the slider block 18, is greater than that of the slope section 15 of the slider located at the outer edge.
The size of the conventional slider is about 4 mm, and these days the size of the slider for a small disk drive unit is about 1 mm. Therefore, because of the dispersion in the size of the sliders, the properties of the magnetic heads are influenced greatly.
An object of the present invention is to provide a method of manufacturing a magnetic head, wherein the warping of the wafer can be prevented. The wafer process and the step of forming the sliders from the wafer can be executed more precisely, and magnetic heads with higher quality and reliability can be manufactured.
In the present invention, the method of manufacturing a magnetic head includes the step of linearly grinding a surface of a wafer, in which a plurality of magnetic head elements are formed on a substrate. The surface of the wafer may be ground by an outer circumferential face of a disk-shaped rotary grind stone, and the width of the outer circumferential face of the disk-shaped rotary grind stone may be 10 mm or more. In this method, the amount and the direction of the warping of the work piece can be controlled, and a direction of grinding traces can be properly selected for further machining.
Further, the surface, which has been linearly ground, may be abraded in a circumferential direction, and this may be done by using a rotating face of a disk-shaped rotary grind stone. In this method, the entire wafer can be uniformly abraded, so that the warping of the work piece can be reduced.
Additionally, if the surface is ground in a direction parallel to a direction of cutting the wafer to form a plurality of blocks, and in each of which a plurality of magnetic head elements are arrange. As a result, stress in the wafer can be released, and the warping of the slider block can be reduced.
The method of the present invention can prevent the warping of the wafer during the wafer process or the step of grinding the wafer. As a result, the present invention improves manufacturing accuracy of the magnetic head, form patterns with higher accuracy, and stabilize the making of shapes and quality of the sliders. Consequently, high quality magnetic heads can be manufactured more stably.